Hi guys were is the best place to buy a pilot jet for a 2007 250 beta rev 3 also im wanting to go one size up from standard so what size will i need , What model mikuni carb does the 2007 rev 3 use

http://www.splatshop.co.uk/catalogsearch/result/?q=Mikuni+pilot

Try the above link for jets or Beta UK. You could also try Yamaha dealers like Nigel Birkett.( Birkett Motorsport)

When I replied to your earlier post about jets I was thinking you had a 125 with a Dellorto.

Carb on an 07 250 should be Mikuni VM26-208 with a 150 main jet and 30 idle / pilot jet.

Thanks dadof2 whats the next size up from a 30 pilot jet

I don't know for sure, looks like it may be a 32.5, see http://www.motocarb.com/mikuni-pilot--air-jets.html